Annealing process

ABSTRACT

Method and apparatus for producing non-friable cast alloy shapes by controllably cooling them after casting. The alloy shapes are gravity fed through an annealing insulated tower at a controllable speed proportional to the rate and degree of cooling required to produce the optimum characteristics for the particular alloy shapes cast, such alloy shapes being ferrosilicon, silicomanganese, ferromanganese and the like.

United States Patent [191 Hard et al. A

[ 1 OCt.8,1974

[ ANNEALING PROCESS [75] Inventors: Robert A. Hard, Lewiston; Loyal A.

Stoyell, Tonawanda; Claude Frank Young, Niagara Falls, all of N.Y.

[73] Assignee: Union Carbide Corporation, New

York, N.Y.

[22] Filed: Aug. 7, 1972 [21] Appl. No.: 278,248

Related U.S. Application Data [62] Division of Ser. No. 883,691, Dec. 10, 1969, Pat. No.

[52] US. Cl 148/3, 75/129, 148/126, 148/157 [51] Int. Cl 822d 25/00, C21d 1/00 Field of Search 148/2, 3, 13, 13.1, 14,

[56] References Cited UNITED STATES PATENTS 1,844,782 2/1932 Mittag 62/314 X 2,166,919 7/1939, Nichols 266/2 2,866,625 12/1958. Sylvest..., 34/33 X 3,197,346 7/1965 Munday 148/l3.l X 3,433,283 3/1969 Montgomery et al. 164/69 3,483,914 12/1969 Farrell et al. 164/69 3,660,081 5/1972 Farrell et al. 75/129 Primary Examiner-Charles N. Lovell Attorney, Agent, or Firm-Frederick J. McCarthy [57] ABSTRACT 5 Claims, 3 Drawing Figures PAYENTEU 0H 8 1974 SPEED MOT 0/? View A -A ANNEALING PROCESS This is a division of application Ser. No. 883,691 filed Dec. 10, 1969 now US. Pat. No. 3,703,039.

FIELD OF THE INVENTION contours, are gravity fed through an insulated tower or tube having a controllable discharge means. The time required for the alloy shapes to flow through the tube I can be automatically regulated by adjusting the discharge means, such time being sufficient to controllably cool the alloy shapes at a rate and to a degree required for the particular alloy cast.

DESCRIPTION OF PRIOR ART Presently, alloy products are cast in large chills and after being cooled to ambient they are crushed by conventional means to produce various alloy shapes. Due to the friability of the alloy, a considerable amount of fines and off-size particles are produced during the crushing operation and subsequently during the transportation of the selected shapes due to the rough and turbulent movements encountered therefrom. These fines and off-size particles are substantially unsaleable and thus decrease the net quantity of selected alloy shapes available for use. Attempts have been made to remelt the fines but this involves an additional operation which increases the overall cost of the alloy shapes.

Another method for producing alloy shapes involves the direct casting of the alloy in molds having predesigned cavity contours. The cast alloy shapes when removed from the molds are air cooled to ambient and then shipped directly to a predetermined location. These alloy castings are still friable and during transit, fines and off-size pieces of the alloy are produced which decreased the net useable quantity of desired alloy shapes.

The advantage of the present invention is that the preferred alloy castings are removed from molds and deliberately cooled at a uniform rate and to a final degree that will produce tough, non-friable alloy shapes which can be transported without breaking up into fines and off-size pieces.

Another advantage is that by using the annealing tower concept of this invention a continuous annealing process is obtained since alloy shapes can be continuously fed into the top of the tower and automatically discharged out at the bottom.

SUMMARY OF THE INVENTION like and an opening at or near the bottom for dischargfor the alloy shapes to flow through the tower can be regulated, such time depending on the rate and the degree to which the particular alloy shapes are to be cooled. For example, 50' percent ferrosilicon alloy shapes should be cooled at a maximum temperature decreasing rate about 1C. per minute until a temperature of about 650C. is reached. Thereafter the ferrosilicon shapes may be exposed to the open air for cooling down to ambient. I

In operation the inside of the annealing tower is initially heated to a temperature above l,0O0C. This is preferably accomplished by placing a bed of insulating material such as vermiculite or sand within the tower and then depositing a first batch of hot alloy castings thereon. The insulating material prevents the heat from the alloy castings from escaping and thus quickly brings the temperature within the tower to above I,000C. ambient. A door blocking the opening at or near the bottom of the tower is then open to a degree necessary to create a draft that can be used to produce a temperature gradient within the tower such that the upper zone or section will be above 1,000C. and the lower zone about 650C. A conventional type compressor may be employed to force feed additional air up through the tower so as to better regulate the temperature gradient within the tower and to maintain a desired cooling rate for the alloy shapes being fed therethrough. If the cooling rate should increase or the temperature gradient change from that desired then a cover may be placed over the top opening and/or the discharge opening may be completely closed since either of which will stop the draft therein thus causing the temperature decreasing rate to slow down. Adjustable size holes may be circumferentially placed on the tower at different height levels with each level of holes being independently operable to bleed some of the air within the tower so that the temperature at any particular height or level can be regulated as desired. Thus by combining these regulatory features incorporated in the tower the temperature gradient can be adjusted and maintained to meet the requirements for annealing'any type alloy castings.v

The insulating material initially fed into the tower is discharged through the lower opening onto a conveyor at a rate sufficient to regulate the passage of the alloy shapes through the tower so that the temperature decreasing rate will not exceed that required for the particular alloy being annealed. Subsequent batches of alloy shapes may then be deposited directly on top of prior batches to provide a continuous automatic annealing process. A bed of insulating material may be added between batches of alloy shapes when the temperature difference between them exceeds about C. It may also be advantageous under certain conditions to add an insulating material at the same time with the alloy shapes so as to form an overall composite that can be fed through the tower at a regulated rate which will insure that the alloy shapes cool no faster than desired. When the cooling occurs at a very slow rate then the compressor can be utilized to increase the air flow through the tower to increase the rate.

BRIEF DESCRIPTION OF THEYDRAAWINGS FIG. 1 is anelevated side view of an annealing tower with a variable speed conveyor.

FIG. 2 is a sectional view of FIG. 1 taken along lines FIG. 3 is aview of the grid selector attached at the end of the conveyor. Y I

Referring to the drawings there is shown in FIGS. 1 and/or 2 a cylindrical tower 1 having an insulating liner 21 made of fire brick, castable refractory or the like all of which is supported by steel brackets 2. On top of the tower a cover, 3 is placed over a receiving opening 4. The bottom portion of the tower is cut at an angle between about 30 and about 60 and preferable about 45 thereby exposing an elliptical shaped opening. lnsulating coverplateS, having an elliptical shape corresponding to the exposed opening, is rigidly secured to the tower wall thus sealing the opening. An arcuate discharge or exit opening 6 is cut into the'lower portion of the longest'wall segment of the tower. Side plates 7 are secured on each side of dischargeopening 6 to provide a restraining orguidingstructure for discharging 'alloy pieces. Insulating cover plate could also be extended somewhat and squared'off to mate with vertical type side plates 7 so as to provide an inclined type extended chute segment- Door 8 is'vertically disposed and slidably mounted on side plates 7 by any suitable means and is shown in a partially opened position. Variable speed'endless belt conveyor9 is driven by motor 10 and located adjacent discharge opening 6.

The angle the conveyor makes with vertical door 8 can vary between about 15 and about 90 and is shown at an angle about 55. v

Screening grid 13,'shown in FIGS. 1 and 3, having parallel side plates 12, is positioned adjacent the end of the conveyor so that'as the alloy shapes are deposited thereon the offsizes 22' will pass through predetermined openings in the grid and fall into container 14 while the desired sizes 11 will be guided into container 15. Thus the annealing process for the alloy shapes is automatic from the time they are deposited into the tower until they are fed into container 15.

At least one level of horizontally disposed bleed holes 20 are circumferentially placed around the tower and mate with holes 18 in annular rings 19. By rotating rings 19, holes 20 can be opened to any degree from a fully closed position to a fully opened position. Air

compressor means could also be connected to holes 20 by suitable conduits so as to force air into the tower at any particular level thereby providing a more regulated cooling apparatus.

In the operational mode, door 8 is closed and a bed of insulating material such as vermiculite or sand is ini-v tially fed into the tower through opening 4 to a height sufficient to at least cover opening 6. Metal cast alloy shapes l1, preshaped in special cavity molds, are introduced through opening 4 onto the bed of insulating material. The heat from the alloy sizes quicklyv increases the temperature within the tower to above 1,000C. ambient. Thereafter discharge door 8 is partiallyopen, if necessary, to provide a draft or convection type air flow within the tower that causes the lower portion of the tower to cool faster than the top portion since the heat rises to the top. When the lower zone of the tower reaches about 650C., the alloy shapes within this zone could then be discharged through opening 6. If the I cooling rate occurs too fast then cover3 is placed over opening 4 or door 8 is closed to terminate the convective air flow. By properly adjusting the convective air flow a temperature gradient can be created within the tower such that a temperature of about 650C. can be maintained in the lower section while a temperature of above l,00OC. can be mainta'inedin the top section. To increase the convective air flow, compression means 16 forces air through holes 17 located in plate cover 5. To regulate the temperature at any particular height within the tower. bleed holes 20 may be open. if necessary, to bleed off some of the convective air flow within or'to force feed air into the tower thus providing a means for producing a temperature gradient within the tower that can be regulated at various levels.

When a temperature difference between alloy shapes within the tower and alloy shapes being added is great then a sufficient amount of an insulating material may be added prior to adding the hot alloy shapes. This will insure that the hot castings will be maintained at the top portion of the tower where the temperature is above 1,000C. for a specified time before being gravity fed through the tower where the, temperature decreases.

The opening of door 8 to different heights also affects the flow rate of the alloy shapes through the tower thus providing an additional means for controllably cooling them.

Conveyor 9 may contain an endless type belt having apertures smaller than the desiredalloy sizes so as to pass only alloy fines and off-size pieces therethrough while conveying the desired alloy sizes to a predetermined collection or depositing point. Off-size pieces EXAMPLE A'cast iron moldcontaining l2 pockets was used to produce truncatedpyramid shapes of 50 percent ferrosilicon to meet a 5- by 2-inch specification, such specification requiring that at least percent of the alloy shapes pass through a 5-inch screen maximum a Xamimum of 10 percent passing through a 6-inch screen and a maximum of l0 percent passing through a 2-inch screen. Several controlled temperature casts from a l,O0O-lb. induction furnace were used in the mold to produce about 3,000 pounds of 50 percent ferrosilicon shapes. A bed of vermiculite was deposited into a 6-foot, 6-inch high annealing tower having an outside diameter of 2 feet and an inside diameter of 20 inches. The lower portion of the tower was cut at an angle of about 45 and an insulating plate was secured to the wall of the tower thus providing an internal inclined surface which would direct material within the tower to discharge opening located at the lower portion of the longest wall segment of thetower. The bed of vermiculite filled the tower and covered the discharge opening in the lower portion of the tower. The 50 percent ferrosilicon shapes were deposited on the bed of vermiculite at a temperature in excess of 1,000C. An adjustable flap was attached to the bottom of the tower (to simulate an endless type conveyor) for regulating the discharge of the vermiculite from the lower openingthus enabling the alloy shapes to be gravity fed through the tower at a rate where they cooled at a maximum rate of 1C. per minute till they reached a temperature of about 650C. It took about 8 hours for the 3,000 pounds of alloy shapes to pass through the tower. The operation of the tower and the simulated conveyor encountered no difficulty and produced 50 percent ferrosilicon shapes having an excellent physical appearance that met the 5- by 2 inch specification as described above with only a l percent reject after being substantial improvement in the saleable end product of 50 percent ferrosilicon sizes as a result of employing the annealing tower apparatus of this invention. In addition the annealing of the alloy shapes is accomplished on an automatic basis wherein a continuous feed of hot alloy shapes are put in one endof the tower and the final annealed shapes are discharged at the other end. Deliberately cooling the alloy shapes at a slower maximum temperature rate than occurs when they are exposed to open air, produces a less friable alloy shape which can withstand the rough handling usually encountered in transit and during unloading at its final destination.

The described method, construction and operation of the preferred embodiment should in no way limit the broad scope of this invention which is set forth in the appended claims.

What is claimed is:

l. A method for producing tough non-friable cast ferroalloy shapes which comprises casting a bath of molten alloy in molds, removing said alloy shapes while hot and placing them in a heat retaining zone to initially raise the temperature in said zone to above 1,000C, said zone being vertically disposed and surrounded by an insulating medium, passing air within said zone in an upward direction so as to convectively create a temperature gradient therein with a high temperature at the top region and a lower temperature at the lower region. and regulating the gravity flow of alloy shapes through the zone so that said alloy shapes will decrease from an initial temperature in excess of 1,000C. to a temperature of about 650C. at a rate not faster than 1C. per minute.

2. The method of claim 1 wherein said alloy shapes are placed into the heat retaining zone together with an insulating material.

3. The method of claim 1 wherein the alloy shapes are automatically discharged from the heat retaining zone upon reaching the lower region of said zone and exposed to the open air for cooling down to ambient.

4. The method of claim 1 wherein insulating material is initially deposited within said heat retaining zone so as to retain the heat of the initial alloy shapes so that said alloy shapes will not cool faster than 1C. per minute.

5. The method of claim 1 wherein said alloy shapes are 50 percent ferrosilicon. 

1. A METHOD FOR PRODUCING TOUGH NON-FRIABLE CAST FERROALLOY SHAPES WHICH COMPRISES CASTING A BATH OF MOLTEN ALLOY IN MOLDS, REMOVING SAID ALLOY SHAPES WHILE HOT AND PLACING THEM IN A HEAT RETAINING ZONE TO INITIALY RAISE THE TEMPERATURE IN SAID ZONE TO ABOVE 1,000*C, SAID ZONE BEING VERTICALLY DISPOSED AND SURROUNDED BY AN INSULATING MEDIUM, PASSING AIR WITHIN SAID ZONE IN AN UPWARD DIRECTION SO AS TO CONVECTIVELY CREATE A TEMPERATURE GRADIENT THEREIN WITH A HIGH TEMPERATURE AT THE TOP REGION AND A LOWER TEMPERATURE AT THE LOWER REGION, AND REGULATING THE GRAVITY FLOW OF ALLOY SHAPED THROUGH THE ZONE SO THAT SAID ALLOY SHAPED WILL DECREASE FROM AN INITIAL TEMPERATURE IN EXCESS OF 1,000*C. TO A TEMPERATURE OF ABOUT 650*C. AT A RATE NOT FASTER THAN 1*C. PER MINUTE.
 2. The method of claim 1 wherein said alloy shapes are placed into the heat retaining zone together with an insulating material.
 3. The method of claim 1 wherein the alloy shapes are automatically discharged from the heat retaining zone upon reaching the lower region of said zone and exposed to the open air for cooling down to ambient.
 4. The method of claim 1 wherein insulating material is initially deposited within said heat retaining zone so as to retain the heat of the initial alloy shapes so that said alloy shapes will not cool faster than 1*C. per minute.
 5. The method of claim 1 wherein said alloy shapes are 50 percent ferrosilicon. 